<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #box {
            border:1px solid #ccc;
            position: absolute;
            left:0;
            right:0;
            margin:20px auto;
        }
    </style>
</head>
<body>
    <canvas id="box" width="800" height="450"></canvas>
</body>
<script>
    //获取canvas
    const boxDom=document.querySelector('#box')
    //生成canvas对象 相当于echarts中的echarts.init(boxDom)
    const context=boxDom.getContext('2d')

    context.lineWidth=10;
    context.strokeStyle='#f00';
    
    

    //context.arc(x,y, 圆半径, 起始弧度, 结束弧度, 是否顺时针);
    context.arc(400,225, 100, Math.PI / 180 * 0, Math.PI / 180 *360, true);
    
    context.stroke();
    
    


    
</script>
</html>